Party official Nadezhda Boltenko said a United Russia lawyer who tried to extinguish the fire at the offices in Novosibirsk was also hospitalized and three other people suffered smoke inhalation, RIA Novosti reported.
The woman, Veronika Gerasimova, who media reports said is between 50 and 60, had sought legal help from United Russia last year, Boltenko said.
Gerasimova had paid for an apartment in a building under construction but thought the completed apartment was subpar and sued the developer, Taiga.info reported.
She lost a court case against the developer, Boltenko said.
Gerasimova had met with party officials Wednesday.
The Moscow Times reported she was apparently upset with advice she received from United Russia and emptied a pickle jar containing fuel over herself and set herself ablaze.
RIA Novosti said real estate developers in Russia frequently swindle prospective landlords who purchase apartments under construction.